Dog has strange growth on leg?

This is about my dog she is some mastiff breed (not sure, I bought her from a hobo) and is 6 years old. So the past 2 months there has been this growth starting to show on her one leg, it looks really disgusting and I don't like to look at her any more. Anyway we have tried to take her to the vet but every time the mexican who works for us tries to pick her up she bites him. Now the mexican wants to sue us because he has been bitten twice and my mother is on the edge, she really wants to shoot the dog (and the mexican, rofl). So do you think it is worth to still try and get the dog to a vet, the growth is pretty large now or to just kill it?